690671561 has 2 divisors, whose sum is σ = 690671562. Its totient is φ = 690671560.

The previous prime is 690671543. The next prime is 690671591. The reversal of 690671561 is 165176096.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 690375625 + 295936 = 26275^2 + 544^2 .

It is a cyclic number.

It is not a de Polignac number, because 690671561 - 2²⁶ = 623562697 is a prime.

It is not a weakly prime, because it can be changed into another prime (690671591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345335780 + 345335781.

It is an arithmetic number, because the mean of its divisors is an integer number (345335781).

Almost surely, 2^690671561 is an apocalyptic number.

It is an amenable number.

690671561 is a deficient number, since it is larger than the sum of its proper divisors (1).

690671561 is an equidigital number, since it uses as much as digits as its factorization.

690671561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 68040, while the sum is 41.

The square root of 690671561 is about 26280.6309094740. The cubic root of 690671561 is about 883.9421797832.

The spelling of 690671561 in words is "six hundred ninety million, six hundred seventy-one thousand, five hundred sixty-one".